The expanding use of engineered nanomaterials (NM) in consumer products and technological applications has spurred environmental and consumer health and safety (H&S) concerns. This project investigates the question of NM skin exposure. We take a systematic approach to quantify effect on NM composition, charge, size on penetration through skin exposed to acute and chronic levels of ultraviolet radiation. Under conditions that NM penetrate skin we will characterize their association with epidermal cells, including antigen presenting cells to establish this as a mechanism of systemic transport. We will determine if and how NM may impact UVB induced immunosuppression and allergic contact hypersensitivity. Finally, we will determine if measuring inside-out water loss from skin is a viable means to assess outside-in NM penetration risk. This project will produce a concise body of work that will aid in assessing risk factors associated with unintentional NM skin exposure and discover novel mechanisms by which NM may impact skin immune function.